OK, you're right. It seems that small form factors (Mini) and all-in-ones (iMac) are generally classified as "desktops". Though workstations (Pros) are not.
By "desktop", I meant "towers, mini-towers, and those horizontal towers that used to prop up CRT monitors". Computers that you could stuff high-end (but not workstation) video cards, and quad core processors into.
It's only recently that the iMac used "desktop" parts, and not "laptop" ones, isn't it?